Interrupt Acknowledge
IACK
13-107
Assembly Language Instructions
Syntax
IACK
src
Operation
Perform a dummy read operation with IACK = 0.
At end of dummy read, set IACK to 1.
Operands
src general addressing modes (G):
0 1
direct
1 0
indirect
Opcode
31
24 23
16
8 7
0
15
0 0 0 1 1
1
src
1
G
0
0
0 0 0 0 0
Description
A dummy read operation is performed if off-chip memory is specified. IACK is
set to 0, regardless of
src location, a half H1 cycle after the beginning of the
decode phase of the IACK instruction. At the first half of the H1 cycle of the
completion of the dummy read, IACK is set to 1. The IACK signal will not be
extended due to multicycle reads with wait states. This instruction can be used
to generate an external interrupt acknowledge. The IACK signal and the ad-
dress can be used to signal interrupt acknowledge to external devices. The
data read by the processor is unused.
Cycles
1
Status Bits
LUF
Unaffected
LV
Unaffected
UF
Unaffected
N
Unaffected
Z
Unaffected
V
Unaffected
C
Unaffected
OVM
Operation is not affected by OVM bit value.
Mode Bit